Tape controlled line spacing and form feed mechanism

ABSTRACT

A high speed printer adapted for serially recording selected characters of a type wheel along the print line of a recording paper mounted on a platen. A line spacing mechanism for accurately turning the platen is driven by a motor for driving the type selection mechanism by way of a power transmission mechanism which is selectively driven according to the command signal for carrying out the desired line spacing operation. To attain stable and accurate operation, a detent mechanism is applied to the power transmission mechanism. A program reader is mounted on the printer in cooperation with the detent mechanism. A fine adjustment of the platen position is also applied to the power transmission mechanism.

United States Patent Kawano et a1.

1111 3,858,704 1 1 Jan. 7, 1975 [75] Inventors: Reijiro Kawano; Kazuhiro Goda,

both of Kawasaki; Hiroshi Yamakawa, Tokyo; Osamu Ohhara, Sagamihara, all ofJapan [73] Assignee: Kurosawa Tele-Communications Limited, Tokyo, Japan [22] Filed: May 23, 1972 21 Appl. No.: 256,124

[52] U.S. Cl. 197/133 R, 197/48, 197/114 R [51] Int. Cl B41j 15/00 [58] Field of Search 197/114 A, 114 B, 114 R, 197/121,122,123,133 R, 48

[56] References Cited UNITED STATES PATENTS 1,143,212 6/1915 Lockwood 197/123 1,564,913 12/1925 Van Duyl 197/133 R 1,951,517 3/1934 Maul 197/114 R 2,555,732 6/1951 Dayger et 111.. 197/133 R 2,766,826 10/1956 Osgood, 197/114 R X 2,860,758 11/1958 Rhodes et al. 197/133 R 2,863,549 12/1958 Kelly 197/133 R 2,884.852 5/1959 Saltz 197/133 R X Andrews et a1 197/133 R 2,910,164 10/1959 3,094,261 6/1963 3,208,575 9/1965 3,280,957 10/1966 3,326,348 6/1967 3,429,414 2/1969 Bradbury 197/114 R X Primary Examine rErnest T. Wright, Jr. Attorney, Agent, or Firm-Maleson, Kimmelman & Ratner [57] ABSTRACT A high speed printer adapted for serially recording selected characters of a type wheel along the print line of a recording paper mounted on, a platen. A line spacing mechanism for accurately turning the platen is driven by a motor for driving the type selection mechanism by way of a power transmission mechanism which is selectively driven according to the command signal for carrying out the desired .line spacing operation. To attain stable and accurate operation, a detent mechanism is applied to the power transmission mechanism. A program reader is mounted on the'printer in cooperation with the detent mechanism. A fine adjustment of the platen position is also applied to the power transmission mechanism.

4 Claims, 7 Drawing Figures PATENTEDJAN W5 3858,7021

SHEET 3 0F 5 PATENTED JAN 7 I975 SHEET 0F 5 PATENTEDJIW H915 3,858,70

SHEET 50F 5 Fig. 7

SUMMARY OF THE INVENTION The present invention relates to an improved line spacing mechanism which can be utilized for a printer. Recently, a requirement has arisen to increase the printing speed of printers used for data communication, peripheral devices of computers, teletypewriters, etc.

Based on the above-mentioned requirement, a number of improvements of the mechanism of the printer have been effected. One of these improvements is directed to improving the function of the type carrier, by an alternative of the well-known conventional type bar mechanism to a type of carrier provided with cylinders or palettes or balls or multi-wheel. Besides this improvement, various mechanisms or type-selection, by which the type carrier provided with a type wheel is displaced so as to select characters, have been developed. However, in the latest printer provided with the abovementioned improvements, such line spacing mechanisms as pawl-feed or segment or a special worm gear mechanism for providing an intermittent driving or rack and pinion systems are still being applied for linespacing the recording paper by utilizing a platen.

Generally, it is required to operate the driving mechanisms for actuation of the type selection mechanism, the line spacing mechanism etc., in a stable and accurate condition. To satisfy this requirement, the motion of the driving mechanism is carried out smoothly and with minimum change of acceleration. With respect to the line spacing mechanism, it is further necessary that the driving connection to the platen is capable of being disengaged so that the platen can be manually operated when the printer is stopped, and the line spacing mechanism must be capable of line spacing over a plurality of lines forwards or in reverse line spacing. Several upto-date line spacing mechanisms have been developed to satisfy the above-mentioned requirements. However in these line spacing mechanisms, not all of the abovementioned requirements can be satisfied. For example, in a line spacing mechanism capable of line spacing over three lines, the mechanism becomes very complex so that it becomes difficult to operate the mechanism in a stable condition, and further it is'necessary to add an auxiliary driving mechanism for the reverse line spacing operation.

The principal object of the present invention is to provide an improved mechanism for line spacing so that the above-mentioned drawbacks of the prior art can be eliminated.

The practical object of the present invention is to provide a unique printer wherein the line spacing operation is carried out by turning the platen which is actuated by a driving source for the type selection mechanism so that the conventional driving mechanism for actuating the line spacing mechanism, whereby the turning angle of the platen is small, is eliminated. By this improvement the driving mechanism of the printer can be simplified so that the production cost thereof can be reduced. In serially recording selected characters of a type wheel along the print line of a recording paper mounted on a platen, after completion of recording characters on the paper, the platen is turned so as to start the next recording operation at the first line of a fresh paper. Inthis turning operation, the first line is sensed in order to stop the above-mentioned turning or spacing operation. This function is referred to as form feed function" (hereinafter called FF). In this operation, special marks are set on two predetermined lines on a recording paper so as to facilitate the spacing of lines without interruption between the abovementioned predetermined two lines; and the spacing operation is stopped by sensing one of the above- .mentioned marks. This function is referred to as vertical tabulate function" (hereinafter abridged to VT). The abovementioned functions are realized as improved functions of the printer so that particular codes are used in the ISO code. To detect the position of FF and VT on the recording paper, several mechanisms are utilized. For example, the following mechanisms are utilized for detecting the FF position.

1. A mechanism for detecting at least one aperture formed at a predetermined position on a continuous set of papers, so as to stop the line spacing operation.

2. A mechanism for stepwisely displacing a paper simultaneously with generating a signal by an electronic counter at each line spacing operation and continuously accumulating these signals, and generating a FF signal to stop theline spacing operation when the accumulated signal reaches a predetermined value.

3. A mechanism provided with a disc having a notch or a cam which cooperates with a platen, a detector for sensing the notch in the disc or a particular position of the cam profile so that the line spacing operation can be stopped according to the signal of the detector.

However, the above-mentioned mechanisms have certain drawbacks. In the case of the first mechanism (1), it is necessary to make an aperture right through the paper and consequently, it is very difficult to set the position of the aperture precisely on the tape. Further, if many papers are used for the operation, it is difficult to coincide the position of the apertures when the papers are superposed, and consequently, it is difficult to coincide the stopping positions of the papers during the FF operation. As the line positions of the papers can be varied to a desired position facing the type position of the printer by employing a fine adjustment of the angular position of the platen, there is a certain possibility of changing the aperture position of the recording paper so as to have it correspond to the detecting posi tion of the aperture.

In the above-mentioned second mechanism (2), the production cost of the electronic counter is very expensive. Beside the problem of cost, there is a further drawback which can not be eliminated. That is, if the platen is manually turned for adjusting the position of the recording paper only, the electronic counter is not actuated so that the position of the aperture in connection with the electronic counter is biased, and therefore, when the electronic counter generates the FF signal, this signal does not coincide with the FF position of the recording paper.

In the above-mentioned third mechanism (3), as the line spacing varies with the variety of the recording paper, it is necessary to change the disc or cam so as to match the recording paper. Further, if the rotation ratio of the mechanism must be changed, it is necessary to change gears, and consequently, the utility of the printer becomes restricted to a particular recording paper.

Therefore, it is a further object of the present invention to provide a line spacing mechanism having an auxiliary mechanism for driving a program reader to control the line spacing operation.

It is a still further object of the present invention to provide a line spacing mechanism having a fine adjustment capability.

Additional objects, features and advantages of the invention will be apparent from the following description and drawing. It should be understood that various modifications may be made which would all be within the spirit and scope of the invention, and that the true measure of the invention is as defined in the hereafter set forth claims:

In the drawing:

FIG. 1 is a perspective view of a printer, with the cover partly cut off to show the line spacing mechanism and carrier mechanism, according to the present invention,

FIG. 2 is a schematic side view of a mechanism for driving the line spacing mechanism shown in FIG. 1,

FIG. 3 is a plan view of the line spacing mechanism shown in FIG. 1,

FIG. 4 is a side elevational view, partly omitted, of the line spacing mechanism shown in FIG. 1,

FIG. 5 is a schematic side view illustrating the program reader together with the line spacing mechanism shown in FIG. 1,

FIG. 6 is an explanatory perspective view of the clutch means utilized for the line spacing mechanism shown in FIG. 1, and

FIG. 7 is a plan view, partly in section, of an auxiliary mechanism for driving a program reader together with fine adjustment mechanism utilized for the line spacing mechanism shown in FIG. 1.

LINE SPACING MECHANISM The line spacing mechanism of the printer according to the present invention is provided with a clutch which transmits the driving power of the type character selection mechanism to the platen, a clutch magnet which actuates the clutch according to a command signal for the line spacing operation, and a detent mechanism which operates means for providing a particular sensation to an operator so as to sense the number of lines spaced by manual operation of the platen when the printer is stopped and provides the stability by which the turning motion of the platen can be stopped in a stable condition. The power of the type character selection mechanism is applied to actuate the line spacing mechanism so that the platen has various desirable functions.

A printer provided with a line spacing mechanism according to the present invention is shown in FIG. 1. In this printer, the line spacing mechanism 1 is driven by the power source for driving a type character selection mechanism (not shown). The type carrier 2 is driven by the same power source as that for driving the type character selection mechanism.

To clarify this driving system, the principle mechanism for driving the line spacing mechanism 1 is hereinafter briefly explained with reference to FIG. 2. In FIG.. 2, a pair of pulleys 5a and 31a are rigidly mounted on a driving shaft 3a ofa motor 3 for driving the type character selection mechanism, which is provided with a shaft 33 extended in parallel to a platen on which recording paper 30 is mounted and a spur gear 34 mounted on the shaft 33 which meshes with a spur pinion gear 35 secured to a supporting shaft 35a of a type carrier 36. The shaft 33 is driven by the motor 3 by way of a pulley 31b which-is secured to the shaft 33 and driven by the pulley 31a and an endless belt 32. A pulley 5b is mounted on a clutch shaft 10 of the line spacing mechanism 1. This pulley 5b is driven by an endless belt'4 driven by the pulley 5a.

Referring to FIGS. 3, 4, 5, 6, and 7, a type selection mechanism (not shown) is driven by the motor 3. The pulley 5b rigidly mounted on the shaft 10 is driven by the motor 3 by way of the endless belt 4. A first clutch wheel 6a is secured to the shaft 10 and a second clutch wheel 6b is slidably mounted on the shaft, 10 so as to be able to slide therealong and to be able to engage or disengage with the first clutch wheel 60. A small gear 11 is rotatably mounted on the shaft 10 and the gear 11 is secured to the second clutch wheel 6b. Consequently, the small gear 11 is driven when the clutch wheel 6b engages with the clutch wheel 6a. The small gear 11 meshes with a detent gear 12 secured on a shaft 13a to which a platen 13 is concentrically connectable so that the platen 13 is driven with the shaft 13a. A rotary clutch magnet 7 controls the sliding motion of the second clutch wheel 6b along the shaft 10 so as to alternatively engage or disengage the second clutch wheel 6b with the first clutch wheel 60. A clutch lever 8 is rigidly mounted on a rotary shaft 7a of the rotary clutch magnet 7 in such a way that a pin 9 mounted on the free end of the clutch lever 8 engages into a groove 6c formed between the second clutch wheel 6b and the small gear 1 1.

Consequently, when the rotary clutch magnet 7 is actuated by a command signal (LF) for carrying out the line spacing operation, the clutch lever 8 is turned in the direction of arrow A (in FIG. 6) so that the second clutch wheel 6b is displaced toward the first clutch wheel 6a, whereby the first and second clutch wheels 60, 6b are engaged. Consequently, the rotation of the pulley 5b is transmitted to the detent gear 12 by way of these clutch wheels 6a, 6b and the gear 11.

On the other hand, a detent lever 14 is turnably supported by a support pin 14b secured to an auxiliary frame 14c of the printer, and a detent roller 16 is turnably supported by the detent lever 14. A tension spring 15 is connected to one free end of the detent lever 14 while the other end of the spring 15 is secured to another auxiliary frame l3b (FIG. 6) so that the detent roller 16 is always urged toward the detent gear 12. The other free end 14a of the detent lever 14 is always engaged on a shoulder of the clutch lever 8 because the detent lever 14 is always pulled by the tension spring 15 so as to turn about the support pin 14b. The shoulder 8a is formed like a cam in such a way that, when the rotary clutch magnet 7 is actuated to engage the clutch wheel 6b with the clutch wheel 6a, the shoulder 8a pushes the free end 14a of thedetent lever 14 upward so as to disengage the detent roller 16 from the recess between adjacent teeth of the detent gear 12, and conversely, when the rotary clutch magnet 7 is deenergized so as to release the above-mentioned engagement of the clutch wheel 6b with the clutch wheel 6a, the shoulder 80 is displaced downward so that the free end 14a of the detent lever 14 moves downward, consequently the detent roller 16 meshes with the recess between other teeth of the detent gear 12. As mentioned above, the motions of the clutch mechanism and the detent mechanism are carried out simultaneously, consequently, there is no interference to provide an additional load to the driving motor 3 during the line spacing operation by the turning of the platen 13.

When the line spacing operation is completed, the rotary clutch magnet 7 is deenergized, the clutch lever 8 returned toward its rest position so that the clutch wheel 6b. is disengaged from the clutch wheel 6a,in other words, the power transmission driving the platen 13 is stopped. Simultaneously, the detent mechanism is actuated in such a way that the detent roller 16 is meshed in the recess between adjacent teeth of the detent gear 12 as already illustrated, and, consequently, the platen 13 is stably stopped at a precise position. During the stopping of the recording operation, the clutch wheel 6b is disengaged from the clutch wheel 6a while the detent roller 16 meshes in the recess between adjacent teeth of the detent gear 12 by the action of the tension spring 15, consequently, the platen 13 is capable of being turned by manual operation and the operator is able to recognize the amount of turning of the platen 13 from the number of recesses between teeth of the detent gear with which the detent roller 16 meshes during the turning of the platen 13.

Asmentioned above, according to the present invention, the line spacing operation is carried out by utilizing the drive power for the type selection mechanism, and further a very effective detent function is created by applying the operations of the clutch mechanism and the detent mechanism simultaneously so that a very precise and stable detent effect can be attained without any additional load on the driving mechanism.

Next, the practical program for line spacing opera tions is illustrated.

In the case where the type character selection mechanism such as the type wheel of the printer is returned to a predetermined home position thereof at the completion of each of the type selection operations (hereinafter referred to as aggregate motion with home position), the program for the line spacing operation is carried out according to the following steps. First, the rotary clutch magnet 7 is actuated so that the clutch wheel 6b'engages with the clutch wheel 6a, and simultaneously the driving power from the motor 3 is transniitted to the platen 13 so as to turn the platen 13 according to the required number of line spaces. Upon completion of this turning of the platen 13, that is,

upon completion of the line spacing operation, the rotary clutch magnet 7 is deenergized so as to disengage the clutch wheels 6a and 6b. Therefore, while the type wheel is returning to the home position, the line spacing operation is no longer performed due to the disengagement of the clutch wheels 6a and 6b.

This operation should be carried out with a suitable timing which does not disturb correct operation of the detent mechanism. Consequently, when the succeeding operation of the type selection mechanism is commenced, no line spacing operation is required.

In the case where the type character selection mechanism of the printer does not return to the home position at the completion of each of the character selection operations but stays at a previous selected position while the succeeding recording operation is carried out (hereinafter referred to as aggregate motion without home position"), it is possible to turn the platen 13 clockwise or counterclockwise about the turning axis thereof by applying either forward or reverse rotation of the driving motor 3, that is the line spacing operation in the normal direction or reverse direction can be carried. In this case, the type carrier 36 of the printer is rotated by the driving motor 3 via the type character selection mechanism while the line spacing operation is carried out. However, the selection of a subsequently desired type character starts after the completion of the line spacing operation.

Also, if the gear ratio between the gear Ill and the detent gear 112 is selected so as to carry out the line spacing operation-in such a way that a spacing of a single line is attained by an extent of turning motion of the driving motor 3 which corresponds to an amount which allows the type character selection mechanism to select tion mechanism is not constant before the command signal for line spacing operation is given, there are certain cases, particularly, in the application of a mechanical type selection mechanism, where it is impossible to rotate the driving motor 3 by a predetermined number of revolutions so as to carry out the line spacing operation. In this case, it is required to return the type selection mechanism to its home position before actuation of the rotary clutch magnet 7. Consequently, when the command signal for line spacing operation is issued, firstly, the type character selection mechanism is re turned to its home position and next the rotary clutch magnet 7 is actuated, by a command signal which commands the carrying out of the desired line spacing operation. Though the type carrier 36 of the printer is rotated via the type character selection mechanism while the line spacing operation is carried out, selection of a subsequently desired type character is not effected. The selection of the desired type character is performed after completion of the line spacing operation.

In the above-mentioned embodiment, rotary clutch magnets are utilized. However, other mechanisms such as plunger type or armature type may be utilized by means of which the effects similar to the rotary clutch magnet 7 can be expected.

FINE ADJUSTMENT MECHANISM FOR THE PLATEN Referring to FIG. 7, the detent gear 112 is provided with a rollet clutch 4H formed inside thereof. A platen knob 18 is rigidly mounted on the shaft 13a at its outer free end portion. The platen 13 is provided with a flange 50 which is concentrically supported by a pair of connecting rods 50a,50b. The platen shaft 13a is slidably engaged with the flange 50 along the axis of the shaft 113a by means of spline engagement. The connecting rods 50a and 50b are rigidly connected to the flange 50 and the platen I3, and the clutch 42 is rigidly connected to the shaft 13a. A compression spring 43 is mounted on the shaft 13a at a position between the boss of the rollet clutch $2 and a bearing 51 which supports the shaft 13a. Therefore, the line spacing operation can be carried out in such a way that firstly the detent gear 12 is driven as already described, then the motion of the detent gear 12 is transmitted to the shaft 13a by way of the engagement of the clutch 41 with the clutch 42, and then platen 13 is driven by way of the spline engagement of the platen shaft 13a with the flange 50. When it is required to operate the fine adjustment, the platen knob 18 is pushed to the right, (as seen in FIG. 7) which displaces the shaft 13a to the right, so that the clutch 41 is disengaged from the clutch 42. The platen 13 can then be turned together with the flange 50 by turning the platen knob 18.

MECHANISM FOR CONTROLLING THE LINE SPACING OPERATION The printer according to the present invention is provided with an auxiliary mechanism for controlling the line spacing operation. This mechanism cooperates with the above-mentioned line spacing mechanism 1 as hereinafter illustrated. FIGS. 5 and 7 disclose this control mechanism.

An intermediate gear 40 is mounted on the shaft 10 in such a way that the gear 11 is connected with the gear 40. A gear 44 meshes with the gear 40, and a sprocket wheel 46 for driving a program tape 47 is rigidly mounted on a shaft 45 of the gear 44. The sprocket wheel 46 is provided with a plurality of pins 46a arranged on the peripheral surface thereof with a pitch which coincides with the pitch of 2.54 mm utilized in the conventional program tape 47. Therefore the program tape 47 can be fed stepwisely with a pitch of 2.54 mm at each turning step of the sprocket wheel 46. On the other hand, a pair of sensing means 48 and 49 are disposed at positions capable of corresponding to apertures 47b and 47c made in predetermined positions of the program tape 47. Therefore, if apertures 47b and 47c are made in the program tape 47 at predetermined FF, VT positions which correspond to predetermined lines on the recording paper 30 (FIG. 2) and the program tape 47 is mounted on the control mechanism so as to be driven by the sprocket wheel 46, an FF or VT position is detected by the sensing means 48 and 49 so that the line spacing operation can be stopped at the predetermined line onthe recording paper 30.'As the sensing means 48, 49 the well-known photoelectric sensing means such a a combination of a light generator with a photo-diode or photo-cell, or a well-known device utilized with the conventional tape reader may be employed.

As the program tape 47, a conventional tape provided with 5 to 8 units width may be used. However, for the purpose of this control mechanism, a tape provided with one or two units is satisfactory for detecting the FF and VT positions. The program tape 47 is mounted on a suitable punching device and a program is made by making apertures 47b, 47c at desired positions by means of operating keys corresponding to particular codes. For example, if a No. 2 bit position of the program tape 47 is to be represented by the FF code, and a No. 5 bit position thereof is to be represented by the VT code, as the No. 2 bit in the ISO code represents STX, while the No. 5 bit represents the code spacingf the program can be made by punching keys of the punching device which correspond to the abovementioned codes. In the above-mentioned preparation, apertures 47b and 470 are made in the program tape 47 at positions corresponding to the FF, VT positions on the recording paper 30, and the number of feeding ap ertures 47 a which are formed in the program tape 47 and are engageable with pins 46a of the sprocket wheel 46 is selected so as to coincide with the steps of the line spacing operation, and the program tape 47 is then formed in an endless tape in such a way that the total number of steps (N), that is, the total number of the feeding apertures 47a coincide with the total number of the spaced lines of the recording paper 30. The above-mentioned endless program tape 47 can be easily made if a sheet of program tape a little longer than the length of the looped program tape 47 is prepared. To prolong the durability of the program tape 47, it is preferable to make an endless program tape 47 which is provided with a plurality of feeding apertures 47a which are a certain integral number times the abovementioned number N.

When the above-mentioned endless tape 47 is mounted on the sprocket wheel 46 of the control mechanism, it is necessary to position the program tape 47 correctly so as to make the FF position, that is, the starting line on the recording paper coincide with the FF detection position 47b on the program tape 47. To achieve this purpose, after setting the recording paper 30 at the correct starting position, the program tape 47 is suitably mounted on the sprocket wheel 46, and next the FF operation is carried out by pushing one or several specified keys which are one or several of the keys 52 (FIG. 1) of the printer so that the tape driving mechanism is driven by the detent gear 12. In this operation, it is necessary to disengage the clutch 41 from the clutch 42 of the above described fine adjustment mechanism. Consequently, the recording paper 30 mounted on the platen 13 is not displaced but the program tape 47 only is'displaced by the sprocket wheel 46.

When the sensing device 48 and 49 detects the aper tures 47b and 470 corresponding to the FF and VT codes, the FF motion is stopped so that the correct positioning of the recording paper 30 and the program tape 47 can be attained.

As mentioned above, the FF, VT positions on the recording paper 30 can be detected by utilizing the above-mentioned program tape 47. Consequently, the FF, VT positions on the recording papers used for various types of continuous forms can be detected by the above-mentioned mechanism for driving the program tape 47, which mechanism is driven by the detent gear 12 utilized for the line spacing operation by the platen 13. The above-mentioned mechanism is usually referred to as a program reader."

What is claimed is: 1. In a printer for serially recording selected characters of a type wheel along two print lines of a typewriting paper mounted on a platen provided with a platen shaft, by means of a type character selection mechanism driven by a motor, an improved line spacing mechanism comprising:

a first shaft rotatably mounted to a side-frame of said printer in parallel condition to said platen shaft;

intermediate power transmission means for continuously transmitting driving power of said motor to said first shaft;

clutch means for selectively transmitting driving power of said first shaft to said platen shaft; means for actuating said clutch means in accordance with a command signal for carrying out a line spacing operation, said clutch means comprising a first clutch member rigidly mounted on said first shaft and a second clutch member mounted on said first shaft, said second clutch member being axially slideable and rotatable with respect to said first shaft, said second clutch member being engageable and disengageable with respect to said first clutch member responsive to said command signal and said actuating means; and,

a pinion mounted on said first shaft, said pinion being axially slideable and rotatable with respect to said first shaft, said pinion being connected to said second clutch member, said platen shaft having a detent gear secured thereon in engaging disposition with said pinion.

2. An improved line spacing mechanism according to claim 1 wherein said actuating means is a rotary clutch magnet provided with a shaft, said shaft of the rotary clutch magnet for rigidly supporting a clutch lever which controls the engagement and disengagement of said first clutch member with said second clutch member, said detent gear being selectively engageable with a detent roller where said engagement is controlled by a turning motion of said clutch lever of said rotary clutch magnet whereby said detent gear is disengaged from said detent roller while said second clutch member engages with said first clutch member and is alternatively engaged with said detent roller when said turning motion of said clutch lever is completed.

3. An improved line spacing mechanism according to claim 1, wherein said actuating means is a rotary clutch magnet provided with a shaft, said shaft of the rotary clutch magnet for rigidly supporting a clutch lever which controls the engagement and disengagement of said first clutch member with said second clutch member.

4. An improved line spacing mechanism according to claim 1, in which said platen shaft is arranged to be axially slidable by manual operation while maintaining an integrally rotatable connection with said platen, and wherein said platen shaft is further provided with a fine adjustment mechanism comprising a first rollet clutch member formed inside of said detent gear and a second rollet clutch member rigidly mounted on said platen shaft and a helical spring always urging said second rollet clutch member to engage with said first rollet clutch member, a platen knob rigidly mounted on a free end of said platen shaft, whereby, when said platen knob is pushed toward said platen said second rollet clutch member is disengaged from said first rollet clutch member so that said platen can be turned by turning said platen knob. 

1. In a printer for serially recording selected characters of a type wheel along two print lines of a typewriting paper mounted on a platen provided with a platen shaft, by means of a type character selection mechanism driven by a motor, an improved line spacing mechanism comprising: a first shaft rotatably mounted to a side-frame of said printer in parallel condition to said platen shaft; intermediate power transmission means for continuously transmitting driving power of said motor to said first shaft; clutch means for selectively transmitting driving power of said first shaft to said platen shaft; means for actuating said clutch means in accordance with a command signal for carrying out a line spacing operation, said clutch means comprising a first clutch member rigidly mounted on said first shaft and a second clutch member mounted on said first shaft, said second clutch member being axially slideable and rotatable with respect to said first shaft, said second clutch member being engageable and disengageable with respect to said first clutch member responsive to said command signal and said actuating means; and, a pinion mounted on said first shaft, said pinion being axially slideable and rotatable with respect to said first shaft, said pinion being connected to said second clutch member, said platen shaft having a detent gear secured thereon in engaging disposition with said pinion.
 2. An improved line spacing mechanism according to claim 1 wherein said actuating means is a rotary clutch magnet provided with a shaft, said shaft of the rotary clutch magnet for rigidly supporting a clutch lever which controls the engagement and disengagement of said first clutch member with said second clutch member, said detent gear being selectively engageable with a detent roller where said engagement is controlled by a turning motion of said clutch lever of said rotary clutch magnet whereby said detent gear is disengaged from said detent roller while said second clutch member engages with said first clutch member and is alternatively engaged with said detent roller when said turning motion of said clutch lever is completed.
 3. An improved line spacing mechanism according to claim 1, wherein said actuating means is a rotary clutch magnet provided with a shaft, said shaft of the rotary clutch magnet for rigidly supporting a clutch lever which controls the engagement and disengagement of said first clutch member with said second clutch member.
 4. An improved line spacing mechanism according to claim 1, in which said platen shaft is arranged to be axially slidable by manual operation while maintaining an integrally rotatable connection with said platen, and wherein said platen shaft is further provided with a fine adjustment mechanism comprising a first rollet clutch member formed inside of said detent gear and a second rollet clutch member rigidly mounted on said platen shaft and a helical spring always urging said second rollet clutch member to engage with said first rollet clutch member, a platen knob rigidly mounted on a free end of said platen shaft, whereby, when said platen knob is pushed toward said platen said second rollet clutch member is disengaged from said first rollet clutch member so that saiD platen can be turned by turning said platen knob. 